1. Field of the Invention
The invention relates in general to a method for balancing molding flow during the assembly of semiconductor packages, and more particularly to a method for balancing molding flow during the assembly of semiconductor packages with defective carrying units.
2. Description of the Related Art
In the light increasing the production capacity and reducing the manufacturing costs, the chip carrier is designed to have a number of carrying units capable of carrying a number of chips in the manufacturing process of more and more semiconductor packages. The chip carrier can be a substrate of a Ball Grid Array package (BGA package) of a quad flat non-lead package (QFN package). However, during the manufacturing or delivery of the chip carrier, it is not guaranteed that each carrying unit is a good part. Once the chip carrier is detected to have a defective carrying unit, normally, a good chip is not attached to the defective carrying unit in the packaging process, thus forming an empty space. Consequently, during molding, the problems of the bonding wire sweep, the substrate warpage or the mold flash might occur due to imbalanced molding flow. To avoid the above problems, a dummy chip needs to be attached to the defective carrying unit of the chip carrier to resolve the problem of defective packages due to the imbalance of molding flow of the molding compound during the manufacturing process.
Firstly, referring to FIG. 1A, a chip carrier 10 is provided. The chip carrier 10 includes a number of good carrying units 11 and at least a defective carrying unit 12. The chip carrier 10 has a front surface 13 and a rear surface 14. The rear surface 14 has a membrane 15 pasted thereon. Further referring to FIG. 1B, a number of chip glues 20 are formed on the good carrying units 11 and the defective carrying unit 12 of the chip carrier 10. Next, referring to FIG. 1C, a number of chips 30 are attached to the good carrying units 11 of the chip carrier 10. Referring to FIG. 1D, a dummy chip 40 is attached to the defective carrying unit 12 of the chip carrier 10. Further referring to FIG. 1E, a number of bonding wires 50 are used to electrically connect the chips 30 and the good carrying units 11. Referring to FIG. 1F, a molding compound 60 is formed on the chip carrier 10 to seal the chips 30 and the dummy chip 40. According to the above manufacturing process, the dummy chip 40 must be obtained first, and then the dummy chip 40 is attached to the defective carrying unit 12 to avoid the occurrence of defective product due to imbalanced molding flow when the molding compound 60 is formed via molding. However, higher manufacturing costs are involved.